Why my cordless kettles stop creating contact after 1-2 years

I have had various models of cordless kettles over the years and they all seem to fail to make electrical contact with their base plate sometime in the 12-24 month range. For a period of time I am able to turn the kettle left or right and create a contact, but this becomes more intermittent over the space of a month or two until it stops working at all. As far as I can tell, both the controls and the heating elements are still functioning correctly - it is just that the contact between kettle and base fails. I have tried using emery paper to shine the contact points but neither kettle or base plate looks corroded. Current and past model giving problems are Breville variable temp models